Acid Block Anion Membrane Proton Leakage
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Solution Overview
Problem
Proton leak through anion selective membranes in bipolar electrodialysis processes leads to poor anion transfer current efficiency, low acid and base concentration, and high energy costs due to the Grotthuss mechanism.
Innovation Solution
Development of an acid block anion selective polymeric membrane with a woven or non-woven cloth reinforcing structure, prepared by copolymerization of ethylenically unsaturated aliphatic or aromatic tertiary or quaternary amine monomers, cross-linking monomers, and vinylbenzyl chloride, with a free radical polymerization initiator, in the absence of a non-polymerizable solvent, resulting in a membrane with reduced water content and increased cross-linking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anion selective membranes are used in bipolar electrodialysis, then the membrane structure is simple and easy to manufacture, but proton leakage occurs through the Grotthuss mechanism resulting in poor current efficiency
Solution Approach 1:
The patent applies composite materials by combining polymeric matrix with inorganic particles (such as metal oxides or ceramic materials) to create a hybrid membrane structure. This composite approach reduces proton leakage pathways while maintaining anion transport functionality, achieving current efficiency greater than 93% by blocking the Grotthuss mechanism pathways that cause proton contamination in conventional polymeric membranes.
2Productivity
If anion selective membranes with high anion transfer efficiency are used, then acid and base concentration is improved, but H+ migration through the membrane increases due to the Grotthuss mechanism
Solution Approach 1:
The patent applies local quality by creating regions with different properties within the membrane structure. Inorganic particles are distributed throughout the polymeric matrix to create localized zones that selectively block proton transport while allowing anion passage. This local modification of membrane properties enables high anion transfer efficiency with reduced proton leakage, achieving current efficiency greater than 93%.
Solution Approach 2:
The patent utilizes porous materials by incorporating inorganic particles with controlled pore structures that physically block the continuous water networks required for Grotthuss mechanism operation. The porous inorganic phase creates discontinuous pathways for protons while maintaining sufficient porosity for anion transport, thereby improving productivity by reducing proton contamination in the acid and base streams.
3Reliability
If membranes with reduced water content and increased cross-linking are used, then H+ migration is retarded and current efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-synthesizing inorganic particles with appropriate pore structures and surface properties before incorporating them into the polymeric matrix. This pre-preparation of functional particles simplifies the overall manufacturing process compared to attempting to create the complex cross-linked structure through in-situ polymerization, making the membrane fabrication more manageable while achieving the desired reduced water content and high current efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The membrane achieves a current efficiency of greater than 93% and effectively retards H+ migration, enhancing the electrodialysis process by improving acid and base production efficiency and reducing energy costs.
Implementation Method 1
copolymerization of components of (I) an ethylenically unsaturated aliphatic or aromatic tertiary or quaternary amine monomer, (II) a cross-linking monomer, and (III) vinylbenzyl chloride in the presence of a free radical polymerization initiator
Implementation Method 2
H+ migration across the anion select membrane has proven problematic. This proton leak through the anion selective membrane is well known and is referred to as the Grotthuss mechanism by which protons diffuse through the hydrogen bonding network of water molecules
Implementation Method 3
When a direct electrical current is applied to the bipolar membrane, water is split into OH− ions and H+ ions which migrate to the anode and cathode respectively
Implementation Method 4
water is split into OH− ions and H+ ions which migrate to the anode and cathode respectively
Implementation Method 5
The cation selective membrane readily allows passage of the cations (positively charged ions, such as Na+, H+) therethrough while blocking passage of anions
Implementation Method 6
the anion selective membranes readily permit passage of the anions (negatively charged ions, such as Cl−, OH−) while retarding cation migration
Data Source
AI summary
Acid block anionic selective polymeric membranes are provided of the type having a woven or non-woven cloth reinforcing structure. The polymer of the membrane is prepared by the process comprising copolymerizing components I, II, and III wherein I is an ethylenically unsaturated aliphatic or aromatic tertiary or quaternary amine monomer. II is a cross-linking monomer, and III is vinylbenzyl chloride. The reaction is conducted in the presence of a free radical polymerization initiator. Additionally, anionic exchange membranes of the type used in electrodialysis apparatus are disclosed and comprise a woven or nonwoven cloth that is impregnated with a copolymer comprising the reaction products of components I, II, and III.